- #1
buttersrocks
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Homework Statement
(Goldstein 3.3)
If the difference [tex]\psi - \omega t[/tex] in represented by [tex]\rho[/tex], Kepler's equation can be written:
[tex] \rho = e Sin(\omega t + \rho) [/tex]
Successive approximations to [tex]\rho[/tex] can be obtained by expanding [tex]Sin(\rho)[/tex] in a Taylor series in [tex]\rho[/tex], and then replacing [tex]\rho[/tex] by its expression given by Kepler's equation. Show that the first approximation by [tex]\rho[/tex] is given by:
[tex] tan \rho_1 = \frac{e Sin(\omega t)}{1-e Cos(\omega t)} [/tex]
and that the next approximation is found from:
[tex] sin^3(\rho_2 - \rho_1) = -\frac{1}{6}e^3 sin(\omega t + \rho_1)(1+e cos(\omega t))[/tex]
Homework Equations
All shown above...
The Attempt at a Solution
Okay, the first part quickly pops out of the Maclaurin series for Sin(rho). The second part, however, I'm having some trouble with. I can think of many different ways this might be approximated and don't know which approach the book is looking for. If someone could set me on the right track, I'd very much appreciate it. (the e^3/6 is making this look like they want me to use the next term of the taylor series or something.)
Methods I can try:
Expand the taylor series around [tex]\rho=\rho_1[/tex] for the first however many terms. (While this may not be the method the book is looking for, it's probably going to give something more accurate than the maclaurin series with the same number of terms...)
Take the next term of the Maclaurin series. (I'm getting stuck when doing this.)
Something that strikes me odd, but perhaps he wants some sort of iterative approach using Newton-Rhapson at this point?
Thanks.